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Re: Got Lucky - Right Place at the Right Time

Glad you found the source of the smoke. I think you're supposed to leave the silicone adhesive there, the smoke is to make the light bad azz. Who would want to mess with this...

If I post some lens specs, can someone/some of you provide a starting point for some experimentation to achieve a 1 to 1.5 degree beam and tighter, more intense spot? I conversed for about 20 minutes with someone at Edmunds. Bottom line, they thought I needed a little more magnification via a shorter focal length Plano Convex lens in front.

Specs are close but not exact.

Primary Lens:
40mm diameter
FL - unmeasured at this point
Thickness: 7mm
Curve radius - unmeasured at this point
Depth of concave surface: 4mm
Location: flat surface is 25mm in front of 1" Parabolic reflector focal point and 8.5mm, in front of lamp window exterior surface

3. Add my wild assumption: In a mixed system with Large front lens + small secondary reflector, Assume the small reflector next to light source acts exactly the same as the small lens next to light source in multi lens system, ignore if they are elliptical or parabola & ignore the urge of trying to figure out why.

Prediction:
In a mixed system with Large front lens + small secondary reflector, one would predict that the lux is dictated by the front lens diameter only. In such case, as long as you do not increase the front lens diameter, you will not increase the lux (beyond quality improvements).

Re: Got Lucky - Right Place at the Right Time

As a laymen in this arena, I think I understand what you've said. But as a laymen again, it seems that if everything else remains the same, a front lens that focuses the same amount of light input out the front in a smaller beam, will produce a smaller and brighter spot down field.

Re: Got Lucky - Right Place at the Right Time

For the most part as ma_sha1 said, changing the lens without going with a larger aperture won't gain more lux, just a different beam profile. There may be some lux gains by tweaking the lens to accommodate the non-uniform source area and non-uniform luminance profile of the source, but it would take some serious experimentation or computer modeling to extract that bit of optimization. The light may already be optimized since some thought had gone into the design. I'd be surprised if less than a 2-degree beam could be had from such a small design, that's pretty darn good.

EDIT: I'm also confused by this design; using a parabolic reflector to a lens, so I'm kinda staying out of this one. A parabolic already makes the light as parallel as it can, the lens can't make it any more parallel. Maybe the lens is just for flood mode. Maybe see what you get without the lens.

Re: Got Lucky - Right Place at the Right Time

Originally Posted by BVH

.....as a laymen again, it seems that if everything else remains the same, a front lens that focuses the same amount of light input out the front in a smaller beam, will produce a smaller and brighter spot down field.

I am a layman, but I suspect a smaller beam will give a brighter spot for this light. The same lumen on a smaller area results in higher lux.

Ma_Sha is probably right in essence. But there are details we don't know and its behaviour we can not predict.
Its to simple to make a parallel comparison between led-and-aspheric and XSA-and-multi-lens-system.
This MegaRay is optimized for a certain behaviour.
Now you have to find out how with a given diameter you can optimize the Cermax for tightest beam and throw. With or without using the exisiting components.

There are free modelling apps online, have found multiple but the links are lost in my archives. Most free tools are limited to one or two lenses by the way.
I am sure if you find multiple white papers addressing 'focusing light by using reflector and lenses', you will soon get more grip.
Thanks for the details and the laserjobs for measurements, I might reconstruct it in cad in time for my knowledgebase or I don't know why. Its an effective solution.
I am sorry I can't do Raytracing as in light-engineering software.

Re: Got Lucky - Right Place at the Right Time

I've got some cheap "test" Plano Convex lenses coming from Anchor which is owned by Edmunds. They are not the perfect shorter Focal Length steps I would like but all are a little less diameter and shorter focal lengths none the less so we'll see what happens. I have a Perkin Elmer Cermax bulb bench power supply with ignitor for 175 and 300 Watt bulbs and I have a 300 watt Cermax Parabolic light module and made hi voltage cables for the connection. I can play around with this setup very easily with just the lamp and some of the test lenses to see the result without the Plano Concave lens. Maybe the concave lens is just for flood as mentioned above.

Re: Got Lucky - Right Place at the Right Time

With solid state lasers, the light emitted from the cavity produces a tiny spot that diverges very quickly. The beam is then expanded and recollimated. All else the same, it seems like beam diameter and divergence are inversely proportional; the larger the beam diameter, the lower the divergence. Maybe this will help you brains think.

Edit: Another laser "device" that might translate well to this application is a beam expander. If you focus a theoretical laser to infinity and send it through a beam expander, the beam is expanded and then recollimated, using two complementary lenses (one concave, the other its matching convex). The result on the theoretical laser is a wider beam diameter. The result on actual lasers is that it is easier to bring the divergence down, and you can achieve lower divergences than you can with the non-expanded beam.

Re: Got Lucky - Right Place at the Right Time

Originally Posted by get-lit

I'm also confused by this design; using a parabolic reflector to a lens, so I'm kinda staying out of this one. A parabolic already makes the light as parallel as it can, the lens can't make it any more parallel. Maybe the lens is just for flood mode. Maybe see what you get without the lens.

I guess the point is that it's not one lens but two, this smaller visible one and the second in the front tube only shown in earlier pics.
In connection they have both input and output parallel and just widen the beam (and they allow slight modification for flood).

Re: Got Lucky - Right Place at the Right Time

Originally Posted by Walterk

I am a layman, but I suspect a smaller beam will give a brighter spot for this light. The same lumen on a smaller area results in higher lux.

It's not the same lumen on a smaller area. Different focal lengths of the same aperture will generally change the beam diameter AND amount of light within the beam. The longer focal length will gather less light but collimate better, a smaller beam with less light. A shorter focal length will gather more light but will not collimate as well, a larger beam with more light; but generally with the same "concentration" of light.

My hunch is that since the parabolic reflector collimates the light, and since it can't be be further collimated after that, then the lenses actually de-collimate the light for flood use. What sven_m says makes perfect sense. I can't conceive of how this could otherwise work.

Re: Got Lucky - Right Place at the Right Time

Originally Posted by get-lit

It's not the same lumen on a smaller area.

Still believe, thinking of input and output, assuming equal efficiency in the system, the Lumen collected from the arc by the Cermax reflector is the same, the projected spot is smaller, thus higher lux.

Re: Got Lucky - Right Place at the Right Time

Here's my take - There's two cases here...

Case 1. If the Cermax is an ellipsoidal, which we already gather it's not, the lumen gathered by that Cermax reflector is always the same, but a longer focal length lens for greater collimation is placed further back and thus utilizes less of the light gathered by the Cermax reflector; and conversely, a shorter focal length lens would be placed closer to the Cermax reflector and gather more of its light while the shorter focal length would reduce collimation; wherein the net effect either way is the same beam intensity of different pattern, aside from somewhat minor advantages when optimizing for the lamp source area dimensions and luminance distribution pattern.

Case 2. If the Cermax reflector is parabolic, as we understand it is, no lens is going to improve the beam, neither in collimation nor light gather.

Re: Got Lucky - Right Place at the Right Time

It's like bshanahan14rulz said, it's a beam expander. Collimated beam in, collimated beam (with bigger diameter) out. The fun however is: While the beam diameter (at the lens) increases, the divergence decreases. To be more precise: The product of lens area (A) times beam divergence solid angle (Omega) is constant for a beam throughout an optics system. That's what my avatar image means

Like Walterk said, that implies that the light from the parabolic reflector is projected into a smaller spot of higher intensity.

And like ma_sha1 said, reflector and concave lens together work like a precollimator, increasing caught luminous flux [lumens] and producing a wider beam, but with the same spot intensity (compared to a setup without reflector and concave lens): Spot intensity (and thus throw) depends on front lens area and source luminance (which isn't changed by the lens system); to get more throw you'd need a bigger front lens or a brighter (in terms of luminance) arc.

(The above does not account for losses due to absorption, reflection (at lenses), scattering or imperfect lenses/reflectors.)

Re: Got Lucky - Right Place at the Right Time

This is very interesting, but my observation is that the light from the parabolic can not be better collimated.

Divergence from the parabolic reflector does not emmenate as angular distribution from a single point as in Dr.Jones avatar, but from every single point within the entire surface area of the parabolic. Therefore, if a lens were to improve collimation for a point on the parabolic surface, it would greatly hinder collimation from all other points on the parabolic surface.

I think in this application, the lens is to apply controllable beam spread to the light from the parabolic. If BVH compared lux readings with the parabolic/lens combo and a parabolic/flat glass combo, the parabolic/flat would be marginally brighter.

Re: Got Lucky - Right Place at the Right Time

Not sure precisely what you'd like to see but I can say this. With only the Plano Concave/rear lens in-place, there is no hotspot visible at all at about 10' distance. If I light up my 300 Cermax bulb by itself, It yields a hotspot maybe 14" in diameter at 10'. When I place only the Plano Convex/front lens in front of it and focus it as tight as it will go, the hotspot seems more intense and is about 8" in diameter. I haven't removed the concave lens from it's factory position yet. Once I do, I will be able to provide more info. Another project (new thread here in HID Section) has my attention currently and my bench is only so big.

Re: Got Lucky - Right Place at the Right Time

10 feet is much too close to see collimating effect. The lens is simply spot focusing up close rather than collimating. Need a long distance comparison, outdoor beamshots with and without the lens.

The light from the parabolic does not diverge as if emanating from a point...

I wish it did because that would open new doors to what could be accomplished, but instead it diverges from every point on the parabolic surface...

For illustration, lets split the opposing divergences into red and blue lines...

Now if a lens were to increase collimation for the blue lines, it would decrease collimation for the red lines (and vice versa)...

The lens is not increasing collimation for any benefit at distance, but rather it's spot focusing it up close, and generating a usable flood at distance.

The Megaray is using an adjustable spaced pair of Plano Convex lenses to create an adjustable flood from the collimated light from the parabolic.

Also, just to be absolutely sure you're dealing with a parabolic lens rather than an ellisoidal, turn on the lamp with just reflector and move a flat object from a rather large distance to right up to the reflector aperture. If you notice the beam get smaller than the aperture at any point in between, it's ellisoidal. If not, it's parabolic. I'll be dumbfounded if it's parabolic and the lens somehow does increase collimation at long distance.

Re: Got Lucky - Right Place at the Right Time

My avatar is only a simplified image Those ray cones are supposed to emanate from all points of the surfaces A1 and A2.

In #136 you try to apply only one lens - that can't work. You need to use two lenses.

Let's consider arc and reflector as a secondary light source, already quite collimated, as in your 4th image; it's aperture (reflector front) is a disc emitting light with some amount of divergence.
In the simple simulation below that's the green circle. The white rays shown are only the "most divergent" rays that go upwards, like your red and blue rays, but just the upward ones. Their angle is the divergence angle for the beam from arc+reflector.
The beam expander shown is not to scale (it's a simple simulation; also the front lens is too small and needs to be bigger to catch all the rays), but it works: A parallel beam goes in, a parallel one comes out. The point is: The angle of those most divergent rays has become smaller, i.e. the divergence is reduced.

Re: Got Lucky - Right Place at the Right Time

Thanks Mr.Jones for taking the time to explain that. It's an interesting method to increase collimation. However, it don't see how it may circumvent the trade-off we always have to accept with differing configurations of the same aperture... you either get more collimation with less total light output, or you get less collimation with more total light output, with relatively the same final beam brightness either way. As the configuration in the diagram increases collimation, it does so at at loss of more than half the total light output, so it would seem the final beam brightness would be relatively equivalent to other configurations of the same aperture.

BVH, could you take an outdoor long distance beamshot of the light with the lenses and without the lenses? That would really help determine what's occurring and if there's a way to improve.

Re: Got Lucky - Right Place at the Right Time

BHV: Doesn't make a difference in this simple simulation; the plano-convex and plano-concave lens helps reducing aberrations a bit (but that simulation uses 'perfect' lenses anyway).

get-lit: That HID light doesn't loose total light output like the optics in the simulation, because it uses a much bigger front lens to catch all the light from the concave lens. So the trade is that you get better collimation at the price of a bigger lens - so it finally comes down to what ma_sha1 said: With a given source, throw is determined only by front lens diameter (and losses...).

Re: Got Lucky - Right Place at the Right Time

Now there's an ah-ha moment for me... I didn't realize the lens aperture was larger than the parabolic reflector aperture. I'd still like to see how it compares long distance with and without the lens.

Re: Got Lucky - Right Place at the Right Time

That's a huge difference. No reason to bother with more beamshots to figure this out. This is a method I'd never seen before in a searchlight, and I've researched all of them, so I thought. The Megaray is definitely something to be proud to have in your arsenal.

Re: Got Lucky - Right Place at the Right Time

Originally Posted by get-lit

............... The Megaray is definitely something to be proud to have in your arsenal.

I am but......I always want MORE! I'm really focused on getting the 500 Watt+ Short ARC Light Cannon working. I've wanted the 500 Watt Spectrolab Starburst for ages and this will be my chance, and in a smaller package that really is handheld'able

Re: Got Lucky - Right Place at the Right Time

I confirmed that the bulb in my Megaray is the Parabolic Cermax PE175BF. I did this by removing the lens holding band on the front of the bulb, carefully cutting the bead of silicone sealant holding the yellow silicone donut to the Cermax bulb ceramic body, then rolling the donut off the bulb. Lastly, carefully, by hand/finger, removing all the silicone sealant residue off the ceramic body, ensuring every tiny bit was off. Removing the band allowed me to see the part number on the bulb. According to the mfg, the donut is there to prevent flashover during starting. This is because the lens holding band was manufactured too wide and when installed correctly, it effectively narrows the gap between Cathode and Anode because it slides on beyond the Cathode lamp terminal band. When I reinstalled the lens holding band, I moved it forward (towards the front of the light) by about 1/32" from where it was. According to the mfg, this will not significantly affect the optics performance. I started the light and was able to verify that there is no flashover occurring after 10 starts, cold and hot. I have not re-assembled the light yet because I want to do some more focusing investigating so I'll have to wait to see if the magic smoking issue is fixed by removing the silicone donut and sealant. See post 120 and this will make better sense when looking at the pic.

Re: Got Lucky - Right Place at the Right Time

The instructions that came with the lamp advised to run it the first time for between 1 and 2 hours but didn't say anything further about minimum run times. Something to the effect that this establishes the point on the Cathode from which the arc will form in future runs to minimize future flicker (movement of the arc to different points on the Cathode)

Re: Got Lucky - Right Place at the Right Time

It's always cautioned to run for longer in the manuals for larger lamps (Strong and Spectrolab user manuals), but maybe it's because they have much higher ignition voltages for igniting larger gaps, which in turn may deform the electrodes more with each ignition. A bit OT, but my mishap with 50kv a while back put a nice dent in the nickel reflector it arced against and vaporized a thin temp probe lead. Literally turned the entire lead to gas in a single pop.

Re: Got Lucky - Right Place at the Right Time

Yes, It's scary sometimes working with 10's of KV! No matter how careful I am, I still make mistakes. Just the other day, I plugged the input cables of my FMC PL8 battery charger in reverse polarity. As plain a mistake as one can make. Thank goodness that charger was programmed with many, many safety algorithms and all it does is beep at me when something like this happens. But it just reinforces the fact that no matter how careful a person is, mistakes will be made.